A new study finds that many Caribbean coral reefs have either stopped growing or are on the brink of erosion.

An international team of researchers has discovered the amount of new carbonate added by Caribbean coral reefs is less than half of what was produced some 1,000 years ago. In some habitats, it is 70 percent lower. Coral reefs produce and gather calcium carbonate, a key ingredient essential for the corals to grow vertically. The decrease in the availability of calcium carbonate is impacting the growth potential of reefs, said the researchers.

For their study, the research team compared the modern day growth rates of reefs with the rates measured in the region over approximately the last 7,000 years. They found that the growth rates of reefs in waters of around five-meter depth have reduced by 60-70 percent when compared with the regional averages taken from historical records. The reef growth rates have reduced by 25 percent in waters of around 10 meters in depth.

Reefs in key habitats need a minimum of around 10 percent of living coral cover to maintain their structures. However, some coral reefs are below this threshold and are at a greater risk of erosion.

Previous studies have already suggested that Caribbean coral cover has shrunk by around 80 percent on an average since the mid-1970s. Habitat destruction, pollution, disease and rising sea temperatures are the main factors contributing to the decline. It is only expected to intensify as a result of future climate change, according to the researchers.

"It is most concerning that many coral reefs across the Caribbean have seemingly lost their capacity to produce enough carbonate to continue growing vertically, whilst others are already at a threshold where they may start to erode," lead researcher Chris Perry, of the University of Exeter, U.K., said in a statement.

"At the moment there is limited evidence of large-scale erosion or loss of actual reef structure, but clearly if these trends continue, reef erosion looks far more likely. Urgent action to improve management of reef habitats and to limit global temperature increases is likely to be critical to reduce further deterioration of reef habitat."

The findings of the study appear in the journal Nature Communications.